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HK: Physik der Hadronen und Kerne

HK 17: Electromagnetic and Hadronic Probes II

HK 17.2: Gruppenbericht

Dienstag, 9. März 2004, 16:00–16:30, B

First measurements of transverse spin asymmetries at COMPASS — •Richard Webb¹, Jens Bisplinghoff², Franco Bradamante³, Wolfgang Eyrich¹, Horst Fischer^4,5, Rainer Joosten², Anna Martin³, and Paolo Pagano³ — ¹Physikalisches Institut, Friedrich-Alexander-Universität Erlangen-Nürnberg — ²Helmholtz-Institut für Strahl- und Kernphysik, Universität Bonn — ³Università degli Studi and INFN, Trieste — ⁴Albert-Ludwigs-Universität Freiburg — ⁵CERN, Geneva

COMPASS is a fixed target experiment on the SPS M2 beamline at CERN. Its ⁶LiD target can be polarised both longitudinally and transversally with respect to the polarised 160GeV µ⁺ beam. Approximately 20% of the beam-time in 2002 and 2003 was spent in the transverse configuration. The analysis of semi-inclusive deep inelastic events in transverse mode opens up a number of channels to investigate the transverse quark distribution function Δ_T q(x) and its associated structure function h₁. One of these is the azimuthal asymmetry in single pion production, the so-called Collins effect. During the 2002 beam time COMPASS collected approximately 1.2 · 10⁷ tranversely polarised SIDIS events, enabling a first determination of the Collins asymmetry. Preliminary results of this analysis will be reported. This work was supported by the BMBF.